I have a Bull Mastiff, she is a beautiful dog and they are usually quite big ( mine isn't very big) they do say that when you buy a bull mastiff for the first time it should be a bitch as dogs are a little harder to handle. you should really check them out and if you want any advice feel free to ask me..
Here is a video not sure how to embed sorry. It shows that they are obedient
https://youtube.com/watch?v=L-Pzk...ADC2050BF42F5B